Magnetic storage devices store data on magnetic media using write heads that generate small magnetic fields. As a write head passes over a medium, its small magnetic field alters localized magnetic moments on the medium. Data is retrieved from magnetic media using read heads that sense transitions in the localized magnetic fields generated by each of these magnetic moments. In response to each of these transitions, a read head generates electrical pulses that are part of a series of pulses forming a read signal. The pulses are either positive or negative depending on the direction of the magnetic moment transition.
Ideally, each pulse rises and falls quickly to provide a very sharp and large peak for detection. Unfortunately, capacitive and inductive effects and magneto-resistive head effects often cause shouldering just before or just after the peak. In extreme cases, this shouldering can be detected as a peak and can cause some data to be obscured. In addition, noise in the read channel often interferes with proper peak detection.
Prior art systems have attempted to remove noise and shouldering from the pulses using fixed filters that are designed to produce the best average pulses for an entire line of magnetic storage devices. However, these fixed filters are unable to accommodate pulse idiosyncracies that are found in individual data storage devices within a line of data storage devices. In addition, in disc drives, such fixed filters are unable to accommodate changes in the pulse shape that occur because the head has moved to different radial positions along the disc.
The present invention addresses these and other problems, and offers other advantages over the prior art.